The passage of the The 1901 Act outraged real estate interests. They felt that the law "came unannounced and unheralded upon an unsuspecting real estate public like a thunderbolt from a clear sky," and were shocked by the way they felt that its passage had been "railroaded through the Legislature." Oppositon to the new law focused on the belief that it would inhibit the construction of new buildings and that the required improvements would increase owner's expenses and lower rent rolls in older buildings. In March, 1901, the Real Estate Record and Builders Guide, a weekly magazine that generally expressed the interests of the real estate community, editorialized against the proposed law:

Maintaining, as we have always done, that the solution of the tenement house problem can be found rather in encouraging the building of tenement houses than by discouraging it; and being strongly averse to any experimental increases in the public expenses at the present time, we feel compelled to oppose the bills of the Tenement House Commission.

The editorial went on to decry the loss of rentable space that would result if the law were passed, warned that builders might stop developing tenements and invest their money elsewhere, suggested that the new tenements required by the law might not be marketable, and criticized the expense of establishing a tenement house department.

However, by 1902, even the Real Estate Record had grudgingly agreed that the law was not as dire as had been predicted, noting that new law tenements "can be made to yield almost if not quite as good a return as the houses formerly built on a single lot" and that the requirements, with regard to older buildings were "with one exception [i.e., toilets]...trivial and would cut but a small figure in an investment calculation." In the following year, the magazine was even more emphatic, sneering at the remaining oppositon to the law, primarily on the part of Brooklyn and Bronx owners, and declaring that "it is creditable to the tenement-house builder of this Borough [Manhattan] that he is not more active in the present oppositon , and it is one of the strongest evidences of the practicality of the new law that it has converted its chief and most weighty opponents so speedily....[T]he measure has been found to be a sane, moderate, workable reform."